Photographic process and product



United States Patent Ofilice 3,114,636 I HOTOGRAPHIC PROCESS AND PRODUCTEdwin H. Land, Cambridge, Mass, assignor to Polaroid Corporation,Cambridge, Mass, a corporation of Delaware No Drawing. Filed Apr. 21,1961, Ser. No. 104,513 6 Claims. (Cl. 9629) This invention relates tothe formation of photographic images by diffusion transfer processes,and particularly to processes wherein the surface of a diffusiontransfer image is after treated with a liquid coating composition.

The formation of transfer images by diffusion transfer processes is nowwell known. The formation of silver transfer images, wherein an exposedsilver halide emulsion is developed and a soluble complex of unexposedsilver halide is transferred to a superposed image-receiving layer toprovide a silver transfer image is described in a number of patents;see, for example, U.S. Patent No. 2,543,181, issued to Edwin H. Land onFebruary 27, 1951; US. Patents Nos. 2,698,237, 2,698,238 and 2,698,-245, all issued December 28, 1954, to Edwin H. Land; US. Patent No.2,774,667, issued December 18, 1956, to Edwin H. Land and Meroe M.Morse; US. Patent No. 2,823,122, issued February 11, 1958, to Edwin H.Land; etc. Color images also may be formed by diffusion transferprocesses; see, for example, the aforesaid US. Patent No. 2,543,181;U.S. Patent No. 2,559,643, issued to Edwin H. Land on July 10, 1951; US.Patent No. 2,661,293, issued to Edwin H. Land on December 1, 1953; U8.Patent No. 2,774,668, issued on December 18, 1956, to Howard G. Rogers;US. Patent No. 2,968,554, issued January 17, 1961 to Edwin H. Land; thecopending US. application of Edwin H. Land and Howard G. Rogers, SerialNo. 565,135, filed February 13, 1956; and the copending US. applicationof Howard G. Rogers, Serial No. 748,421, filed July 14, 1958 (now US.:Patent No. 2,983,606 issued May 9, 1961).

It is frequently desirable to apply a liquid coating composition to adiffusion transfer print to improve its stability, and particularly toprotect the surface of the print from the hazards encountered inhandling and storage, such as dirt or dust, fingerprints, scratches, andthe like. Such a photographic transfer image ordinarily retains at leasttraces of photographic reagents with which it has been processed, thecontinued presence of which may adversely affect the quality andstability of the image. For example, the oxidation products of somesilver halide developing agents tend to oxidize silver and thus maycause a loss of density in a silver transfer image.

Reaction products from residual sodium thiosul-fate also may actadversely by oxidizing silver. In addition, oxidation by atmosphericoxygen of unreacted developing agent or other components of theprocessing composition may impart a stain or otherwise discolor atransfer image, particularly the highlights thereof, whether the imageis composed of silver or dye. Application of the liquid coatingcomposition is effective to render such residual processing reagentsrelatively inocuous, and also may physical-ly remove such residualreagents by a washing action, particularly water-soluble residualprocessing reagents. If parting a physical protective layer to thesurface of the image, may also increase the glossy appearance of theprint.

It has been found convenient and more eflicient, when applying such aliquid coating composition, and particularly one which includes apolymeric material, to employ an applicator such as that disclosed inUS. Patent No. 2,768,403, issued to Charles A. Govatsos on October 30,1956. The applicator comprises a substantially rigid holder and anabsorbent element retained within the holder. The absorbent element maybe of any appropriate Patented Dec. 17, 1963 absorbent material whichwill serve to retain a quantity of the liquid coating composition, andmay be of cotton or wool in any form, such as woven or nonwoven fabricor felt or a batt of such material. The mass of the absorbent element ispreferably proportioned so that it can contain a volume of liquidcomposition suflicient to coat a plurality of photographic prints as,for example, the number of prints obtained from one roll of film. Inuse, a quantity of the liquid composition is applied to the photographicprint by squeezing or applying pressure to the holder portion of theapplicator, and the liquid composition is spread over the surface of thephotographic print by passing the absorbent element portion of theapplicator over the surface of the print while in frictional pressurecontact therewith. A number of such coating compositions particularlysuitable for use with silver transfer prints have been disclosed; see,for example, US. Patent No. 2,719,791, issued October 4, 1955, to EdwinH. Land; U.S. Patent No. 2,794,740, issued June 4, 1957, to Edwin H.Land and Milton Green; US. Patent No. 2,830,900 issued April 15, 1958,to Edwin H. Land, Elkan R. Blout and Howard C. Haas; US. Patent No.2,855,298, issued October 7, 1958, to Edwin H. Land; U.S. Patent No.2,866,705, issued December 30, 1958, to Edwin H. Land and Meroe M.Morse; and US. Patent No. 2,874,- 045 issued February 17, 1959, to EdwinH. Land. Examples of coating compositions useful in imparting aprotective action to color transfer images are disclosed in thecopending US. application of Howard G. Rogers, Serial No. 93,309 filedMarch 6, 1961.

It has been found that while these coating compositions do provide adesirable protective action, the benefits of applying the coatingcomposition are dependent to a substantial degree upon the efiioiencywith which the user applies the liquid coating composition to thetransfer image. While the user may believe that he has in fact uniformlyapplied the composition over the entire surface, it may happen that theamount of the liquid coating composition applied was insufficient, orthat the quan tity applied was not so distributed as to properly coatthe transfer print despite what visually may appear to 'have been auniform application. In addition, it is desirable that the border areasalso be coated with the liquid coating composition to insure that thecorner areas of the image area have been coated, and also to avoid anypossibility of introduction of contaminants into the border areas fromwhich they might diffuse laterally into the picture area to adverselyaffect its quality or stability. In addition, the user may simply forgetto apply the print coating composition.

It has now been found that the efliciency of the print coating operationmay be substantially increased by incorporating a visual indicator,removable by the liquid coating composition, in or on the surface of theimagereceiving layer. Accordingly, primary objects of this invention areto provide an improved process for applying a liquid coating compositionto a dilfusion transfer image and to provide an image-receiving elementparticularly useful in such after coating processes.

Other objects of the invention will in part be obvious and will in part"appear hereinafter.

The invention accordingly comprises the several steps and the relationand order of one or more of such steps with respect to each of theothers, and the product possessing the features, properties and therelation of elernents which are exemplified in the following detaileddisclosure, and the scope of the application of which will be indicatedin the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description.

In accordance with this invention, a colored reagent serving as a visualindicator or guide to the efficacy with which a liquid coatingcomposition has been applied is incorporated in or on theimage-receiving layer of the image-receiving element. The presence ofthis colored reagent serves as a visual reminder to the user to applythe liquid coating composition and also serves to indicate theuniformity and thoroughness with which the liquid coating compositionhas been applied. This colored reagent is present in a substantiallyuniform concentration to give an overall coloration, and preferably is adye which is photographically inert in the particular transfer process.While this dye may be included in the imagereceiving layer, in apreferred embodiment the dye is included in a stripping layer coatedover the image-receiving layer. The use of such stripping layers tofacilitate separation of the image-receiving layer from thephotosensitive layer and the layer of processing composition is wellknown in the diffusion transfer art; note, for example, US. Patent No.2,759,825 issued to Edwin H. Land on August 21, 1956, as Well as each ofstripping layer 15a in FIGURE 1 of the previously mentioned US. PatentNo. 2,719,791, FIGURES 2 and 3 of the previously mentioned US. PatentNo. 2,774,667, and FIGURE 3 of the previously mentioned US. Patent No.2,823,122.

The visual indicator, or coating guide, may be a dye or other coloredsubstance.

While the dye may be of any desired color, it preferably is of a coloresthetically acceptable as a tint in the normally white border areas ofthe transfer image. It is a feature of this invention that the coatingguide dye is removed from the image areas of the image-receiving layerduring imbibition and formation of the transfer image. As a result, theseparated transfer print has a normal appearance except for the coloredborder areas. The dye preferably is removed from the image areas byvirtue of its solubility in the alkaline processing composition. In thepreferred embodiment the dye does not undergo a color change ordecomposition during imbibition, but is merely dissolved out of theimage-receiving element into the processing composition. It will beunderstood, however, that, where desired, one may use dyes which undergoa color change in alkaline environment, or which are bleached orotherwise chemically reacted to yield fragments which are colorlessand/or soluble in the transfer processing composition. It will beapparent that if the dye used as the coating indicator is one whichundergoes a chemical reaction in the presence of the alkaline processingcomposition, the resulting prduct(s) should have no adverse effect uponeither the formation of the transfer image, or upon its stability shouldthey remain in the transfer print. Since the alkaline processingcomposition does not come into contact with the border areas of theprint (by virtue of a mask as is well known in the art), the dye in theborder areas is unaffected and remains to act as a visual indicator andreminder that the protective liquid coating composition has not beenapplied.

It is frequently desirable, particularly where the aftertreatment of thetransfer image with a liquid coating composition serves at least in partto wash out residual photographic reagents, to pass the applicator overthe surface of the transfer image several times, e.g., 4 or 6, and, morepreferably 6 to 8 times, to insure that an adequate treatment has beenaccomplished. A plurality of passes of the applicator also serves tominimize the po sibility that areas of the transfer print will not becoated in any individual pass. It therefore is a further feature of thisinvention that the amount of dye used and/or the solubility of said dyein the coating composition are so adjusted or selected that the desiredminimum number of passes of the print coater must be made in order toremove the dye from the border areas of the transfer print. It will beapparent that the quantity of dye may be readily varied, and that theamount of any given dye necessary to provide the desired color levelwill vary with the spectral efiicieney (e) of the respective dye. Theamount of dye used is preferably just sufficient to impart a clearlyvisible but relatively light tint, so that it will be estheticallyacceptable.

As an example of an embodiment of this invention, 23 g. of a dye sold byGeneral Aniline & Film Co., Bingharnton, N.Y., under the trade name WoolGreen BSNA (Extra Concentrated) were added to 5 gallons of a gurn arabicstripping layer coating composition. The resulting image-receivingelement had a light blue tint. When processed in a silver transferprocess in accordance with the previously noted patents, the image areaof the separated transfer print was substantially completely free of anycoloration from the Wool Green BSNA dye, while the border areas of theprint retained the same blue tint as before processing. Several passesof a liquid coating composition, such as one of those disclosed in theaforementioned patents for aftertreatment of a silver transfer image,removed the dye from the border areas of the print also. Examination ofthe print coater showed a blue coloration of the absorbent cottonbatting, indicating that the dye was not destroyed or otherwise reactedduring the print coating treatment.

Wool Green BSNA is the trade name of General Aniline & Film Co.,Binghamton, N.Y., for a dye having the structure:

'03s on q CH3 NaOaS U H N+ H3O CHa This dye is listed in the ColourIndex, 2nd edition, 1956, as C.I. Acid Green 50 and as C.I. .4090.Transfer prints made using image-receiving elements containing this dyein the strip coat and aftercoated in the usual manner showed nodifference in image stability in accelerated aging tests as comparedwith similar prints made without the blue dye in the strip coat.

Image-receiving elements containing useful concentrations of the WoolGreen BSNA were found to exhibit a reflection density at 650 my.(measured above a magnesium carbonate standard) of from 0.10 to about0.45. The preferred reflection density was about 0.25.

As an example of another dye which has been found useful in thisinvention, mention may be made of Pontacyl Green SN-Extra, C1. No. 737(Colour Index, 1st edition). Other dyes useful in this invention will beapparent or may be readily determined by simple experiments.

The advantages of the incorporation of a print coating guide dye weredemonstrated in two experiments. In the first of these experiments, twosets of 896 silver transfer images were print coated. One set was madeusing an image-receiving element which contained no dye or other visualcoating guide, and 230 of these prints were found to have beeninadequately coated. By comparison, only 43 of the 896 transfer imagesmade on an image-receiving element containing the Wool Green BSNA dyewere found to have been inadequately coated. In the second experiment,480 silver transfer images were made on each of the aforementioned typesof image-receiving elements. 83 of the transfer prints made on thenormal image-receiving sheet were found to have been inadequatelycoated, but only 8 of the pictures made on the Wool Green BSNA coloredreceiving sheet showed any print coating defects.

The efiiciency with which the dye is removed from the image-receivingsheet will be enhanced if the dye exhibits a preferential affinity forthe absorbent material of the print coater, for the film-formingmaterial, e. g., carboxymethyl cellulose or hydroxy ethyl cellulose,employed in the transfer processing composition, and/ or for the gelatinor other polymeric materials of the photosensitive element.

It will be noted that the dye incorporated in the imagereceiving sheetas the print coating guide is substantially completely removed from theimage area during formation of the transfer image, and from the borderarea by the aftertreatment with the liquid coating composition. If anyof the dye remains in the image area or in the border areas after thetransfer image has been properly print coated, the amount of theresidual dye is insufficient to give any appreciable visual coloration,so that for practical purposes, the whites are uncolored.

While the invention has been illustrated with respect to a silvertransfer image which is subjected to an aftertreatment with a liquidcoating composition contained in an applicator or print coater, it willbe understood that the invention is also applicable Where theaftertreatment constitutes immersing the separated image-receivingelement in a suitable liquid, for example, as described in the Us.Patent No. 2,662,822, issued December 15, 1953, to Edwin H. Land. Adevice suitable for etfecting such an immersion is disclosed in US.Patent No. 2,873,660, issued to Edwin H. Land and Vaito K. Eloranta onFebruary 17, 1959.

Since certain changes may be made in the above product and processWtihout departing from the scope of the invention herein involved, it isintended that all matter contained in the above description shall beinterpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a process of forming a photographic image by diffusion transfer,wherein an exposed photosensitive emulsion is developed with an alkalineprocessing composition, an imagewise distribution of a diffusibleimageforming component is transferred by diffusion to an imagereceivingelement carrying an image-receiving layer in superposed relationshipwith said photosensitive emulsion to provide a visible transfer image,and said transfer image is subjected to an aftertreatment with a liquidcomposition to remove or render innocuous residual processing reagents,the improvement wherein the image-receiving element containing saidimage-receiving layer also initially includes a substantially uniformlydistributed colored substance, said colored substance is substantiallycompletely removed from the image areas of said imagereceiving elementduring said development and transfer, said colored substance is retainedin the nonimage, border areas of said image-receiving element, and saidaftertreatment substantilly completely removes said colored substancefrom said border areas.

2. A process as defined in claim 1, wherein said difiusibleimage-forming component is a Water-soluble complex of silver halide, andsaid transfer image is a silver image.

3. A process as defined in claim 1, wherein said liquid coatingcomposition is applied to said image receiving element by means of aprint coater including an absorbent material releasably containing saidliquid composition, said colored substance having an affinity for saidabsorbent material.

4. A process as defined in claim 1, wherein said colored substance iscontained in a layer over said image-receiving layer.

5. A process as defined in claim 1, wherein said colored substance isremoved from said image area by being dissolved in said alkalineprocessing composition.

6. A process as defined in claim 1, wherein said colored substance is adye having the structure:

References Cited in the file of this patent UNITED STATES PATENTS UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N0 3, 114,636December l7 1963 Edwin H, Land It is hereby certified that error appearsin the above numbered patent requiring correction and that the saidLetters Patent should read as corrected below.

which, in addition to im column 6 line 4, for "substantilly" readsubstantially line 11 for "image receiving" read image-receiving line 44for "Govastsos" read Govatsos Signed and sealed this 23rd day of June1964.,

(SEAL) Attest:

ERNEST W; SWIDER EDWARD J. BRENNER All'iuSfing Officer Commissioner ofPatents

1. IN A PROCESS OF FORMING A PHOTOGRAPHIC IMAGE BY DIFFUSION TRANSFER,WHEREIN AN EXPOSED PHOTOSENSITIVE EMULSION IS DEVELOPED WITH AN ALKALINEPROCESSING COMPOSITION, AN IMAGEWISE DISTRIBUTION OF A DIFFUSIBLEIMAGEFORMING COMPONENT IS TRANSFERED BY DIFFUSION TO AN IMAGERECEIVINGELEMENT CARRYING AN IMAAGE-RECEIVING LAYER IN SUPERPOSED RELATIONSHIPWITH SAID PHOTOSENSITIVE EMULSION TO PROVIDE A VISIBLE TRANSFERE IMAGE,AND SAID TRANSFER IMAGE IS SUBJECTED TO AN AFTERTREATMENT WITH A LIQUIDCOMPOSITION TO REMOVE OR RENDER INNOCUOUS RESIDUAL PROCESSING REAGENTS,THE IMPROVEMENT WHEREIN THE IMAGE-RECEIVING ELEMENT CONTAINING SAIDIMAGE-RECEIVING LAYER ALSO INITIALLY INCLUDES A SUBSTANTIALLY UNIFORMLYDISTRIBUTED COLORED SUBSTANCE, SAID COLORED SUBSTANCE IS SUBSTANTIALLYCOMPLETELY REMOVED FROM THE IMAGE AREAS OF SAID IMAGERECEIVING ELEMENTDURING SAID DEVELOPMENT AND TRANSFER, SAID COLORED SUBSTANCE IS RETAINEDIN THE NONIMAGE, BORDER AREAS OF SAID IMAGE-RECEIVING ELEMENT, AND SAIDAFTERTREATMENT SUBSTANTILLY COMPLETELY REMOVES SAID COLORED SUBSTANCEFROM SAID BORDER AREAS.